Rotary actuator



Aug. 14, 1962 F. REIMER ETAL ROTARY ACTUATOR 2 Sheets-Sheet 1 FiledMarch 5, 1959 FIGJ INVENTORS Frederick Reimer BY George Hirschberger QATTORNEY Aug. 14, 1962 F. REIMER ETAL ROTARY ACTUATOR 2 Sheets-Sheet 2Filed March 5, 1959 FlG.6

FIG.

v VINVENTORTQ Frederick lRelmer BY George Hirschberger ATTORNEY UnitedStates Fatent Office 3,049,102 Patented Aug. 14, 1962 3,049,102 ROTARYAUIUATOR Frederick Reimer, Wantagh, and George Hirschberger, Syosset,N.Y., assignors to Parameters, Inc., New Hyde Park, N.Y., a corporationFiled Mar. 5, 1959, Ser. No. 797,510 2 Claims. (Cl. 121-97) Thisinvention relates to rotary actuators, such used in servomotor controlsystems, and more particularly to a novel fluid pressure operated rotaryactuator adaptable for direct driving without the interposition ofgearing or mechanical linkage, and having high efficiency, zerobacklash, low breakaway torque, high speed response, superior accuracy,and low size to output power ratio.

Servomotor systems of the mechanical, hydraulic, and pneumatic poweredtypes have found widespread applications in many fields where remotepositioning control is necessary or desirable. Among such applicationsare the positioning of control surfaces of aircraft, missiles, andnautical vessels, as well as the positioning of antennae. Otherapplications include analog computers and instrument control andindicating systems.

For angular positioning, a rotary type of actuator is frequently used.However, such rotary actuators have hitherto required the use of geartrains or lever systems for transmittal of suflicient operating power,particularly with relatively heavy loads. Such interposed gear trainsand other mechanical linkages have had attendant disadvantages, such asgear back lash, friction, heavy maintenance expense, and the like. Inaddition, the gearing or linkage results in less than accurate angularpositioning of the controlled elements, and frequently are characterizedby excessive hunting and lack of stable positioning. The hydraulic andpneumatic systems have also required a large supply and flow of fluid,with resultant bulky conduits and relatively slow response to controlsignals.

In accordance with the present invention, the foregoing difficulties areavoided and accurate, stable angular positioning obtained by a fluidpressure operated rotary actuator of high power to size ratio andcharacterized by small pressure fluid requirements. The positioningaccuracy, due to its ability to drive controlled elements directly, islimited only by the characteristics of the servomotor control valve andthe transducer feedback system used therewith. The friction issubstantially zero, and there are no rubber seals rubbing against movingparts. Hence, its response frequency is equal to that of the fluidpressure servo system with which it is used. The low rate of fluid flowpermits the use of thin wall, small diameter tubing which can be runlike electric wiring.

More particularly, the rotary actuator comprises a three-part casingincluding a circular mounting plate, a cylindrical body, and a circularcover plate, all formed of a ferritic alloy steel, such as Type 416stainless steel. The two plates are pinned and bolted to opposite endsof the body and are coaxially apertured to receive a shaft of the samemetal as the casing elements, this shaft having a fluid tight bearingfit in the coaxial apertures.

The shaft has pinned and bolted thereto a bushing or sleeve, having anaxial length substantially equal to that of the housing, and an arcuatevane of the same axial length as the sleeve, the vane extending, forexample, through an arc of 117 degrees. The outer radius of the vane issubstantially equal to the inner radius of the body.

An arcuate stop is pinned and bolted on the inner surface of the body,and has an axial length equal to that of the body and an arcuate extentof the order of 90 degrees,

for example. The circumferentially spaced ends of this stop are formedwith substantially rectangular, relatively shallow recesses of lessaxial length than that of the body. The mounting plate has spaced fluidpassages each extending therethrough and through one axial end of thestop to communicate each with a different recess.

The recessing of the arcuately spaced ends of the stop provides axiallyspaced abutments on each such end engaged by the outwardly bent ends ofleaf springs clamped to the arcuately spaced ends of the vane cushioningthe vane at each end of its arc of oscillation. Synthetic resin rings orwashers are set in annular channels in the mounting and cover plate andbear against the vane.

For an understanding of the invention principles, reference is made tothe following description of a typical embodiment thereof as illustratedin the accompanying drawing. In the drawing:

FIG. 1 is a perspective view of a rotary actuator embodying theinvention;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a top plan view thereof with the cover plate removed;

FIG. 4 is an axial section view therlethrough;

FIG. 5 is an axial section of the shaft, bushing and vane;

FIG. 6 is an axial sectional view of the body and stop; and

FIG. 7 is a sectional view on the line 77 of FIG. 6.

Referring to FIGS. 1 through 4, the rotary actuator 10 comprises acasing, including a relatively large circular mounting plate 15, acylindrical body 20, and a circular cover plate 30, and a shaft 40mounted in coaxial apertures in plates and 30. All these parts, as wellas stop 25 and vane 45, are of a ferritic alloy steel, such as Type 416stainless steel.

Mounting plate 15 is formed with a series of countersunk apertures 11receiving bolts 12 threaded into bores 21 of body A pair of countersunkapertures 13 receive locating pins 14 seated in body 20. Around theperiphery of plate 15 are apertures 16 to receive mounting bolts for theactuator. For a purpose to be described, plate 15 is formed with a pairof arcuately spaced apertures 17 which are countersunk and tapped as at18.

Body 20 has secured to its inner surface the arcuate stop having anaxial length equal to that of body 20. The arcuately spaced ends of thisrelatively thick stop have shallow substantially rectangular recesses 22forming axial spaced abutments 23, 23 at the end of each recess.Apertures 24, each coaxial with an aperture 17 in plate 15, extendthrough each of the abutments 23 adjacent plate 15, thus connecting therecesses 22 to apertures 17. The arcuate extent of stop 25 may be of theorder of 90 degrees in a typical exemplary embodiment of actuator 10.Pins 26 and bolts 27 fixedly locate and position stop 25 on the innersurface of body 20, and secure the stop to the body, as best seen inFIG. 6.

Cover plate 30 has countersunk apertures 31 receiving locating pins 32extending into apertures in body 20 and countersunk apertures 33receiving securing bolts 34 threaded into passages 28 in body 20' andcoaxial with passages 21.

Shaft has substantially fluid tight bearing engagement in coaxialapertures 41 and 42 in plates 15 and 30, respectively, one end of theshaft being substantially flush with the outer surface of mounting plate15. The other end 43 of shaft 40 extends beyond cover plate 30 and issplined, formed with a keyway, flattened, or otherwise appropriatelyformed for direct connection of the operated component thereto.

Between plates 15 and 30, shaft 40 has a bushing 44 thereon whose axiallength is substantially equal to that of body'. The vane 45, which may,in a particular example, have an arcuate extent of substantially 117degrees is placed coaxially on bushing 44. The bushing and vane arepositioned on shaft 40 by locating pins 46 and bolts 47. Bushing 44 hasan outer diameter such that it has only running clearance with the innerarcuate surface of stop 25. Similarly, vane 45 has an outer diametersuch that it has only running clearance with the inner surface of body20.

Operating fluid under pressure is selectively applied to the arcuatelyspaced ends of vane 45 by means of nipples 35 screwed into threaded andcountersunk portions 18 of passages, apertures, or ports 17 in plate 15.In turn, these ports communicate with ports 24 in stop '25, and thuswith recesses 22. The fluid under pressure between adjacent ends of stopand vane 45 rotates the vane and shaft 40 in a selected direction, theopposite recess 22 of stop 25 being at exhaust pressure.

As the leading edge of vane 45 approaches the exhaust edge of stop 25,its engagement therewith is cushioned by leaf springs 50 clamped to thearcuately spaced edges of vane 25 by clamp plates 51 and bolts 52,springs 50 having outwardly bent ends 53 engageable with abutments 23.Leakage of fluid around shaft 40 is inhibited by Teflon gaskets 55seated in annular grooves 56, 57 in plates 15 and respectively andengaging the ends of bushing 44. Due to the self-lubricatingcharacteristics of the gaskets 55, there is substantially no resistanceto rotation of vane 45 and shaft even though the gaskets maintain afluid tight seal inhibiting leakage around the shaft.

While stop 25 and vane have been shown and described as positioned onand secured to body 20* and shaft 40, respectively, by means of locatingpins and bolts and,

in the case of vane 45, involving the bushing 44, it should beunderstood that this method of positioning and securement is exemplaryonly. .For many applications, the stop and vane may be secured inposition by brazing or welding techniques, for example. In the case oflow torque actuators, shaft 40 and vane 45 can be machined from a singlepiece of metal.

axially apertured end walls; a shaft rotatably mounted in said end wallsand projecting outwardly of atleast one end wall for direct securementof a positionable component thereto; a radially extending vane, having atruncated sector shape radial section, secured to said shaft Within saidhousing; said vane having an axial length substantially equal to thedistance between said end walls and an outer radius substantially equalto the radius of the inner cylindrical surface of said housing; aradially extending stop, having a truncated sector shape radial section,secured to project inwardly from such in ner cylindrical surface, saidstop having an axial length substantially equal to the distance betweensaid end walls and a radial extent substantially equal to that of saidvane; means for introducing fluid under pressure between a selected oneof the radial edges of said stop and radial edge of said vane; said vaneextending from a tubular sleeve, telescopically secured on said shaftand having an axial length substantially equal to the distance betweensaid end walls; means forming a fluid tight seal between the ends ofsaid sleeve and said end walls; each radial edge of said stop having anelongated recess therein less than the axial length of the stop, theinner surface of each recess lying in a plane substantially parallel toa radial plane of said shaft and the side surfaces of each recess lyingin planes perpendicular to the axis of said shaft; said fluidintroducing means comprising a pair of substantially rectilinearpassages each extending longitudinally through one end wall,substantially parallel to the shaft axis, and through the substantiallyrectangular abutments defining one end of each recess.

2. A rotary actuator as claimed in claim 1 including a pair of leafspring each secured to extend axially of a radial edge of said vane andhaving outwardly bent ends engageable with the abutments defining theends of said recesses.

References Cited in the file of this patent UNITED STATES PATENTS695,006 Stowell Mar. 11, 1902 1,671,254 Porter May 29, 1928 1,717,699Lippert June 18, 1929 1,974,775 Gorsuch et al. Sept. 25, 1934 2,025,573Collingham Dec. 24, 1935 r 2,444,391 Whitfield June 29, 1948 2,633,105Lasater Mar. 31, 1953 2,795,212 Shafer June 11, 1957 2,798,462 Ludwig etal. July 9, 1957 2,854,956 Hager Oct. 7, 1958

